<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 新增的表单标签 -->


    <!-- 
        datalist 必须和input配合使用
        实现可输入的下拉菜单效果 
    -->
    <input type="text" list="a">
    <datalist id="a">
        <option>1</option>
        <option>2</option>
        <option>3</option>
        <option>4</option>
    </datalist>
</body>
</html>